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i <br /> i <br /> w. <br /> 4 .0 FIELD INVESTIGATION <br /> c-a <br /> The first phase of the field investigation program was based <br /> primarily an that proposed (and approved by both Anheuser- <br /> Busch, and the San Joaquin Local Health District ) in the <br /> Contamination Assessment .Flan, dated June, 1987 (ESE, 1987 ) • " <br /> During the field investigation program, which took place <br /> during the week of July 6, 1987, the first monitor well, M14-1 , <br /> located northeast of the excavation area was installed. It 's <br /> approximate location is shown in Figure 4-1 , with a scaled <br /> sketch presented in the Appendix. <br /> F <br /> The second phase of the investigation took pla-ce from <br /> September 3 through September 3, and included the installation <br /> of 19W-2 and M14-3, whose locations are similarly shown in <br /> Figure 4-1 . <br /> F <br /> ,During well construction, soil and ground water samples were <br /> 1 t <br /> collected for lithologic description and chemical analyses . <br /> 1 Sampling met�):odology and field investigation results are <br /> summarized in the following sections. <br /> 4 . 1 ;'METHODOLOGY <br /> 4 . 1 . 1 Phase I <br /> ti During Phase I, one monitor well was constructed using mud <br /> rotary techniques. Mud rotary drilling was selected over <br /> hollow stem techniques because flowing sands were suspected in <br /> the area (based on £SE' s drilling experience within: a 10 mile <br /> radius of the site ) . Because rotary drilling stabilizes the <br /> walls of the wells, preventing sands from flowing upwards, it <br /> was presumed that this technique would have the advantage of <br /> assuring a true, depth discrete sample from the depth of <br /> interest . Mad-rotary similarly accommodates the installation <br /> of. a larger, 4 inch diameter 1'611, which may prove <br /> advantageous if site remediation is required. The mud rotary <br /> k 4-1 <br /> C� <br />